The present invention relates to foot-warming systems for boots and, in particular, relates to the use of those types of foot-warming devices in which portions of the device are selectively removable from the boot so as to lighten the weight of the boot when the device is not in use.
In accordance with conventional technology, there are primarily two types of foot-warming devices used in connection with boots. The first type of device is fully integrated on the boot and may include, for example, a battery charger within the heel of the boot which connects, via a power cord, to a heating element located inside the boot. One conventional type of heating element comprises a flat pad which is mounted to lie along the insole of the boot and which includes a serpentine conductor that is sandwiched between flexible plastic layers. With respect to this type of element, an example of which is shown in Baggio et al. U.S. Pat. No. 4,910,881, heat is generated by passing current through the serpentine conductor.
When a foot-warming device is fully integrated on the boot, as in the manner just described, if damage occurs to the device, such as due to shock caused by jarring of the boot, typically the damage cannot be repaired without disassembling the boot, thereby making repair of this type of device prohibitively expensive. Furthermore, the different components of such a device contribute to the total weight of the boot even when the device does not need to be in operation on the boot, such as during the warmer seasons of the year. In order to address this problem of excess weight, it is possible to purchase separate boots for warm- and cold-season usage, but this option is too expensive except for a small minority of users.
To overcome the difficulties just described, foot-warming devices have been developed in which those components most likely to require attention are detachably mounted on the boot. In these devices, typically the battery pack which is used to energize the heating element and sometimes the heating element itself can be completely removed from the boot thereby enabling these primary components to be maintained or stored separately from the boot. In one typical construction, the battery pack is fastened to the exterior of the boot either by a clip that fits over the collar of the boot or by a belt that fastens around the boot neck. With either of these two securement methods, however, there is a tendency for the battery pack to shift its position and to work loose from the boot, so that in order to keep the battery pack on the boot, constant readjustment of the position of the battery pack is required.
With particular regard to those types of boots where the upper portion of the boot is made of a thick and rigid material, such as the molded plastic compound frequently used for ski-boots, an alternative method of securing the battery pack to the boot uses a cavity formed in the rigid upper portion of the boot. The sides of this cavity serve to hold the battery pack in a predetermined position on the boot, thereby eliminating the need for constant readjustment of the battery pack's position. This type of securement method is shown, for example, in Bragagnolo U.S. Pat. No. 4,780,968. However, this method has been regarded as having limited applicability, and an alternative securement method has been sought which can be used not just with boots having rigid and thick uppers but with other types of boots as well, including those having uppers made with thinner layers of nonrigid or semipliable material, such as leather or rubber sheeting. In other words, it is desired that the foot-warming device be adaptable to boots of a wide variety of styles in order to accommodate the widely varying preferences of different users in respect to boots.
An alternative securement method that has been used with boots having both rigid and nonrigid uppers relies on a rigid bracket that is mounted to the outer surface of the boot, which bracket forms a platform for detachably mounting the battery pack. Such a bracket is shown, for example, in Giese U.S. Pat. No. 3,946,193 and in Slenker U.S. Pat. Nos. 4,950,858 and 5,063,690. In accordance with this approach, the front face of the rigid bracket may be shaped so as to conform to a complementary surface on the back side of the battery pack and the rear face of the bracket can either be curved in order to conform to the rounded shape of the outer surface or can be provided with legs in order to space the bracket from the boot. When this type of bracket is used, however, an additional element is introduced between the battery pack and the boot's outer surface so as to cause the battery pack to jut out prominently from the boot. In this position, the battery pack can, in some instances, interfere with hiking or climbing, particularly when the user is crossing rough terrain.
With respect to those mounting structures that hold the battery pack in stationary position on the boot, such as the rigid cavity and bracket structures above described, it is known to provide one or more electrical connectors in predetermined location on such structures so that the battery pack is automatically connected to the heating element when mounted on the structure. Such connectors, however, tend to be adversely affected by the outdoor elements to which they are exposed when the battery pack is not in use. In particular, moisture, grime and even airborne elements can tarnish or gradually corrode such connectors so that, over time, these connectors become less efficient at conveying current to the heating element, thereby diminishing the capacity of the foot-warming device to deliver heat.
A further difficulty with mounting structures of the rigid cavity or bracket type above described is that a severe jolt can be delivered to the battery pack or foot if impact occurs between the battery pack and a heavy external object, such as a jutting portion on a large log or stone. In addition to possibly causing injury to the foot or leg, this type of jolt can damage the internal energy cells in the battery pack so as to cause abrupt failure of the foot-warming device. Although techniques are known for reducing the frequency of such impacts, such as mounting the battery pack along less accessible portions of the boot or providing rigid members on the boot for shielding portions of the battery pack against direct impact, these techniques may involve adding extra weight to the boot and, in any event, do not protect the battery pack against indirect shocks, such as can be transmitted through the boot itself. Furthermore, although it is possible to carry several spare battery packs and to replace damaged battery packs as the need arises, this adds significantly to the weight which the user must carry.
In accordance with the foregoing, a primary object of the present invention is to provide an improved foot-warming system for a boot.
A further object of the present invention is to provide a foot-warming device each of the components of which are able to be mounted on or within the boot in a manner that eliminates the need for repeated readjustment of the device during use.
Another object of the present invention is to provide a foot-warming device having removable portions so that the weight of the boot can be reduced when the device is not in use.
A related object of the present invention is to provide a foot-warming device in which those portions of the device most likely to need attention or repair are easily removable.
Another related object of the present invention is to provide a foot-warming device in which the battery pack of the device is able to be detachably mounted on the outer surface of the boot in such a manner as to protect the foot and battery pack against severe jolts.
Yet another related object of the present invention is to provide a foot-warming device having a removable battery pack, which pack is able to be detachably mounted on the outer surface of the boot without excessively protruding from this surface.
Still another related object of the present invention is to provide a foot-warming device for a boot most of the components of which can be removed without the use of special tools or without the removal of small and easily lost parts.
Another object of the present invention is to provide a foot-warming system in which the foot-warming device, despite use over many seasons, will retain its original heat-producing capacity.
A related object of the present invention is to provide a foot-warming system in which the conductive structures of the foot-warming device are protected against corrosion or other exposure related damage.
Another object of the present invention is to provide a foot-warming device for a boot which can be inexpensively produced so as to add relatively little to the total price of the boot.
Still another object of the present invention is to provide a foot-warming device for a boot which can be adapted for use with boots in a wide variety of styles.